1. Field of the Invention
The present invention relates to an auto-focusing method in a mobile terminal. More particularly, the present invention relates to a method for auto-focusing in a mobile terminal comprising a camera module which can automatically photograph an image in optimum focus when the camera function is used.
2. Description of the Related Art
A camcorder, which is a representative photographing device, functions as a camera for photographing a subject and also as a video recorder.
It is necessary that the photographing device such as a camcorder performs appropriate exposure and focusing operations in order to sufficiently reproduce the image of a subject and to satisfactorily capture a momentary image. The focusing operation of the conventional photographing device such as a camera or camcorder will now be described.
A variety of focusing methods have been widely used according to systems utilized for measuring a distance between a camera and a subject. These systems are classified into an active system and a passive system. Also, the active system is further classified into an ultrasound focusing system and an infrared focusing system, and the passive system is further classified into a contrast recognition focusing system and an eye-controlled auto-focus system.
First, the active system will now be described.
The ultrasound focusing system measures a time delay from an ultrasound transmission time to its echo reception time in order to calculate a distance between a camera and a subject, and automatically adjusts a lens based on the calculated distance in order to perform a focusing operation. The infrared focusing system moves a lens to enable the infrared beam to be reflected from a subject in a scanning mode, and performs a focusing operation using a trigonometric measurement scheme.
The passive system will now be described.
According to the contrast recognition focusing system, both a mirror cooperating with a lens and a fixed lens project an equal image on a visitronic module, the images are added to focus the images on the lens, and a shutter closes. According to the eye-controlled auto-focus system, five focusing points are horizontally arranged in a finder so that a photographer can see and select one of the focusing points at which a desired target subject is focused.
When photographing a moving image, the photographer focuses using the above-mentioned auto-focusing function, and can adjust a zoom-in key and a zoom-out key to capture an image of a main subject currently in motion while constantly maintaining the size thereof, so that the photographer can photograph the main subject while maintaining the size thereof. Therefore, the photographing device such as a camera or camcorder can take a photograph in optimum focus using the auto-focusing systems when photographing a still image or a moving image.
Such a photographing device contains a system having the auto-focusing function to photograph an image through a camera module, while recording an audio signal input through a microphone.
Recently, a mobile terminal having a camera module to photograph a still image and a moving image has been developed. In addition, the mobile terminal having a camera module can record sound using a microphone thereof simultaneously while photographing an image. In such a mobile terminal, a high-performance microphone is built to receive even a very low audio signal.
However, the conventional mobile terminal supports only a normal photographing function to photograph a still image and a moving image, but does not support the auto-focusing function. Therefore, there is a need to have an auto-focusing function in the mobile terminal.
However, in the mechanical assembly of mounting a microphone and a camera module having the auto-focusing function on the conventional mobile terminal, a noise caused by the motion of a lens during the operation of the auto-focusing function may be input through the microphone.
Therefore, there is a problem in that a camera module having the auto-focusing function must be placed away a microphone as far as possible so that the input of a noise can be prevented. Also, such a limitation in a mechanical construction causes another limitation in constructing the interior circuit thereof.